The overall objective of this U54 Cooperative Specialized Research Center proposal is to characterize, at molecular and cellular levels, the hormonal pathways that regulate embryo implantation and fertility. Failure of the fertilized embryo to implant into the endometrium is a major cause of infertility. The Center will support a multidisciplinary group of scientists with a common interest to understand the mechanisms and cellular pathways that control implantation. The rationale for creating such a Center is to direct our concerted efforts toward the identification of endometrial factors whose aberrant expression or function leads to infertility. The achievement of this goal would require a cohesive, highly effective partnership between the basic and clinical scientists, addressing this question with innovative investigative strategies. This would advance our current understanding of the molecular basis of implantation and help identify factors that underlie infertility in women suffering from endometriosis, a common gynecologic disorder. The knowledge gained from these studies should also aid in developing new molecular diagnostic tools for screening endometrial dysfunction and enable targeted therapeutic strategies for the treatment of infertility. The program is comprised of four complementary, synergistic projects: (1) Role of C/EBP Deta in Uterine Decidualization and Implantation, (2) Nuclear Receptor Coregulators in Implantation and Uterine Function, (3) Regulation of Stromal Differentiation and Implantation by the BMP2 Pathway, and (4) Endometriosis as a Clinical Model of Predecidual Dysfunction. Investigators will be aided by two core facilities: Core A: Administrative Core, and Core B: Microscopy Core.